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The invention relates to the prevention and treatment of cancers in animals. More specifically the invention relates to the use of metal chelating materials including, picolinic acid, fusaric acid and their derivatives as pharmacological and/or biological response modifier agents to prevent and treat cancer in dogs, cats, horses and other domestic or exotic animals.
It will be appreciated that hereinafter the use of the term xe2x80x9cresponse modiferxe2x80x9d is intended to encompass all of the intended functions of the invention and method including antiviral, antiinfective, antiinflammatory, anticancer, vaccine and so on. Further, it will be appreciated that the broad term xe2x80x9cantiinfectivexe2x80x9d is intended to include antibacterial, antifungal, antiparasitic functions, as well as actions against any other infective agent or organism including viruses not encompassed by the term xe2x80x9cantiviralxe2x80x9d. It will also be appreciated that the term xe2x80x9cantiinflammatoryxe2x80x9d is intended to include an inflammatory response modifier, including all inflammatory responses such as production of stress proteins, white blood cell infiltration, fever, pain, swelling and so forth. Furthermore, the term xe2x80x9canalgesicxe2x80x9d is intended to include a pain reliever, whether the pain incurred is a result of disease, inflammation, trauma or psychosomatic reaction.
Researchers recently have come to appreciate the role of metal containing proteins in physiological actions and responses including pain, inflammation, proliferative and infectious diseases. Generally speaking, the inventor has studied the important function of proteins having amino acid sequences which bind metals, particularly transition metal ions therein. For example, the inventor has determined the important role zinc finger or zinc ring proteins as hormone-receptor proteins and in proliferative, inflammatory and infectious diseases. Moreover, the inventor has determined the role of other metal ion containing protein complexes, such as the role of iron finger proteins such as iron-finger hormone-receptor proteins in aging and carcinogenesis.
The inventor and others have recognized at least three efficient approaches to inhibiting zinc finger proteins: 1) disruption of the zinc finger by modification of the cysteins which are at least one of the four binding sites for Zn2+ in the zinc finger protein which results in the ejection of zinc ion; 2) removal of the zinc from the zinc finger moiety by specific chelating agents; and 3) specific chelating agents that form a ternary complex at the site of zinc binding on zinc finger proteins, resulting in inhibition of the DNA or RNA binding activity of zinc finger proteins.
Papilloma virus infection results in a number of proliferative diseases in subjects including warts induced by type 4 human papilloma virus (common warts). Moreover, papilloma virus can cause plantar ulcers as well as plantar warts. Human papilloma virus infection of the uterine cervix is the most common of all sexually transmitted diseases. Commonly known as genital warts, this wide spread virus infection is a serious disease that potentially can develop into cervical cancer. Since the virus is permanently present in cells, infection recurs in a significant percentage of patients. In many instances, conization of the uterine cervix is required to remove the infected tissue.
Condylomata acuminata, also denoted genital warts, are benign epithelial growths that occur in the genital and perianal areas and caused by a number of human papilloma viruses (HPV) including types 6,11 and 54. These are low risk viruses which rarely progress to malignancy. However, high risk viruses such as HPV-16 and HPV-18 are associated with cervical intraepithelial cancer.
The actions of HPV are mediated by specific viral-encoded proteins which interact and/or modulate cellular DNA and proteins to produce abnormal growth and differentiation of cells. Two proteins of the HPV viral genome, E6 and E7, are well conserved among anogenital HPV""s and both may contribute to the uncontrolled proliferation of basal cells characteristics of the lesions. The E7 oncoprotein is a multi-functional protein with transcriptional modulatory and cellular transforming properties. The E7 oncoprotein is denoted as a xe2x80x9czinc fingerxe2x80x9d protein because it possesses a sequence motif that is implicated in zinc binding. A strong correlation between zinc binding and the transactivation activity of E7 has been documented. The HPV-16 E6 protein is a xe2x80x9czinc fingerxe2x80x9d protein that binds DNA and may have transcriptional properties such that its function may be dependent upon the formation of zinc fingers. E6 protein can complex with the cellular tumor suppressor protein p53 and it is necessary with E7 protein for the immortalization of primary human squamous cells. Only two proteins of HPV are consistently expressed and integrated in keratinocytes, the E6 and E7 zinc finger proteins. The E6 and E7 proteins are responsible for continuous cell proliferation. About twenty HPVs are associated with ano-genital lesions and all transformed keratinocytes of these lesions contain E6 and E7 zinc finger proteins. The E6 and E7 regulate growth and transformation by interfering with cellular p53 and pRb proteins, respectively. Thus, one should be able to control or cure HPV by inactivating E6 and E7, the critical zinc finger proteins which are required for replication. When replication of the virus is halted, apoptosis of the virally-infected cells must occur. Thus, one can alter the epidemiology of, for example, carcinoma of the uterine cervix by interfering with the function of zinc finger or zinc ring proteins.
Herpes viruses, for example, Herpes Simplex Virus (HSV), has two important viral metalloproteins, a zinc finger protein and ribonucleotide reductase, an iron-containing enzyme, which are necessary for replication and propagation of the viruses. One can alter the course of herpes diseases, such as xe2x80x9cfever blistersxe2x80x9d and genital herpes, by inhibiting the two viral metalloproteins.
The human immunodeficiency virus (HIV) encodes several regulatory proteins that are not found in other retroviruses. The tat protein, which is one of these proteins, trans-activates genes that are expressed from the HIV long terminal repeat and tat is essential for viral replication. The tat protein of the HIV-1 is a zinc finger protein that when added to certain cells in tissue culture, specifically promotes growth. It has been shown that the tat protein of HIV-1 stimulates growth of cells derived from Kaposi""s sarcoma lesions of AIDS patients. Other experiments raised the possibility that tat might act as a viral growth factor to stimulate replication in latently infected cells or alter expression of cellular genes.
The nucleocapsid p7 protein of HIV has been targeted by the inventor for treatment of HIV viral infections. The p7 protein is required for the correct assembly of newly formed virus particles during the viral life cycle. Moreover, the p7 protein contains two zinc fingers that are required for the recognition and packaging of the viral RNA. Because the zinc finger domain is essential for nucleic acid binding, p7 resistant mutants are highly unlikely to occur. Thus, agents that effectively attack the two zinc finger domains of the HIV virus nucleocapsid p7 in vivo will decrease the overall number of viral particles that bud off and exit the cells to infect other cells.
The hepatitis C virus is not integrated with DNA and thus may be vulnerable to attack by specific antivirals. The hepatitis C viruses are dependent upon the Zn 2+ metalloproteinases for specific viral functions. Processing at the C terminus portion of the NS2 protein of hepatitis C virus is mediated by virus encoded protease (metalloproteinases). Modification of the metalloproteinases presents an opportunity for controlling the progression of hepatitis C mediated disease.
It is of interest to note that the breast cancer susceptibility gene BRCA 1 includes a zinc ring domain that are involved in protein-protein interactions or protein-DNA interactions. It also is of interest to note that the zinc ring domain of the BRCA 1 has a 54% sequence similarity and 38% sequence identity with a zinc ring domain encoded by the genome of the equine herpes virus. (R. Bienstock, xe2x80x9cMolecular Modeling of Proteins Structures, Science and Medicine, January/February 1997, p.56).
From the foregoing it appears that it would be beneficial to have a product that can interfere with the formation or action of certain zinc finger proteins or zinc ring proteins to stop the progress of certain virally induced or mediated proliferative diseases or to halt the progress of viruses or malignancies dependent upon zinc finger or zinc ring proteins for their transformation and immortalization. Furthermore, it would be beneficial to provide a product that can halt the growth of other proliferative cells, such as malignant cells by chelating metal ions from zinc-dependent or iron-dependant, transition metal ion (e.g. copper, iron, etc.) dependent proteins, hormones and enzymes necessary for the replication of the malignant cells.
It is among the objects of the present invention to provide agent can retard the growth and proliferation of target cells by blocking the activity of metal ion-containing proteins. The compound that can retard the growth of premalignant and malignant cells such as virally, chemically and spontaneously transformed cells.
The invention also provide a method of halting the function of zinc finger proteins, zinc ring proteins, and other proteins with zinc binding motifs heretofore unidentified by the administration of a zinc chelating agent, both topically and systemically.
The invention provides a method of halting the function of metal containing protein structures containing metals other than zinc, metal-containing ring proteins structures, such as iron-finger or iron-ring proteins and other proteins with metal binding motifs heretofore unidentified by the administration of a metal chelating agent, both topically and systemically.
The invention includes preparations containing chelating agents such as picolinic acid or derivatives thereof that halts the progression of viral infections or proliferative diseases that is non-toxic to normal cells, easy to use, relatively inexpensive and well suited for its intended purposes.
Briefly stated, an agent for the prevention and treatment of cancers in animal subjects, as well as the method of treatment. In the preferred embodiment, the agent is a metal chelating agent such as picolinic acid or derivatives thereof. The invention can be used systemically or topically to prevent or treat cancers. The metal agents bind metal, for example iron or transition metal ions such as zinc required by transcription proteins found in malignant cells. Furthermore the agents directly inhibit or retard angiogenesis thereby restricting blood flow to the cancer.
One embodiment of a topical preparation consists of a solution of the chelator, for example, 0.01% to 99%, preferably 5% to 25%, picolinic acid in an appropriate vehicle, such as deionized water, lotion or so forth, and is applied to the lesion one or two times daily. In another embodiment, the topical preparation consists of an ointment or cream containing approximately 0.5% to 99%, preferably 5% to 20% picolinic acid which is applied once or twice daily to the lesion and to a bandage placed on the lesion.
Various active derivatives that maintain their activity and stability when after systemic administration are provided. Slow release oral formulations can be used to treat diseases for the digestive tract. The active derivatives can be administered orally, parenterally, by inhalation, transdermally or by any other appropriate method to control proliferative diseases, cancers, viral infections, HIV, and any other condition wherein the causative agent includes a zinc-containing protein, whether the zinc-containing protein is a zinc finger protein, a zinc ring protein, or other type of zinc or metal containing structure heretofore unidentified or undetected, wherein the metal containing segment is required for protein stability and configuration.
It will be appreciated that other appropriate chelating materials such as the derivative of picolinic acid, fusaric acid, also may be used. It also will be appreciated that, although 5% to 20% topical preparations of the picolinic acid are described, a broader range of concentrations may be used. For example from approximately 0.001% to 99.9% metal chelating agent may be used. Further, the systemic doses may be altered or adjusted to ranges greater or lesser than those described, depending on toxicity and patient response, without departing from the scope of the appended claims.
Yet another alternative embodiment provides for an antiangiogenesis compound which retards unwanted angiogenesis.